Fuzzing

[!WARNING]

The fuzzing feature is not for production use. Binaries built with this feature must never be deployed to production.

Firecracker includes compile-time helpers for fuzz testing its internals via the fuzzing feature flag.

What it changes

Building with --features fuzzing alters several subsystems to make Firecracker more amenable to fuzz testing:

• TCP Initial Sequence Numbers use a deterministic hardcoded value instead of the usual random ones, so network behavior is reproducible across runs.
• The balloon device processes the stats queue inline rather than relying on the timer-driven path, which is not available during fuzzing.

Building

To build Firecracker with the fuzzing helpers enabled:

cargo build --features "fuzzing"